/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.net;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import org.apache.nutch.plugin.Extension;
import org.apache.nutch.plugin.ExtensionPoint;
import org.apache.nutch.plugin.PluginRuntimeException;
import org.apache.nutch.plugin.PluginRepository;
import org.apache.nutch.util.ObjectCache;

import org.apache.hadoop.conf.Configuration;

/** Creates and caches {@link URLFilter} implementing plugins. */
public class URLFilters {

	public static final String URLFILTER_ORDER = "urlfilter.order";
	private URLFilter[] filters;

	public URLFilters(Configuration conf) {
		String order = conf.get(URLFILTER_ORDER);
		ObjectCache objectCache = ObjectCache.get(conf);
		this.filters = (URLFilter[]) objectCache
				.getObject(URLFilter.class.getName());

		if (this.filters == null) {
			String[] orderedFilters = null;
			if (order != null && !order.trim().equals("")) {
				orderedFilters = order.split("\\s+");
			}

			try {
				ExtensionPoint point = PluginRepository.get(conf)
						.getExtensionPoint(URLFilter.X_POINT_ID);
				if (point == null)
					throw new RuntimeException(
							URLFilter.X_POINT_ID + " not found.");
				Extension[] extensions = point.getExtensions();
				Map<String, URLFilter> filterMap = new HashMap<String, URLFilter>();
				for (int i = 0; i < extensions.length; i++) {
					Extension extension = extensions[i];
					URLFilter filter = (URLFilter) extension
							.getExtensionInstance();
					if (!filterMap.containsKey(filter.getClass().getName())) {
						filterMap.put(filter.getClass().getName(), filter);
					}
				}
				if (orderedFilters == null) {
					objectCache.setObject(URLFilter.class.getName(),
							filterMap.values().toArray(new URLFilter[0]));
				} else {
					ArrayList<URLFilter> filters = new ArrayList<URLFilter>();
					for (int i = 0; i < orderedFilters.length; i++) {
						URLFilter filter = filterMap.get(orderedFilters[i]);
						if (filter != null) {
							filters.add(filter);
						}
					}
					objectCache.setObject(URLFilter.class.getName(),
							filters.toArray(new URLFilter[filters.size()]));
				}
			} catch (PluginRuntimeException e) {
				throw new RuntimeException(e);
			}
			this.filters = (URLFilter[]) objectCache
					.getObject(URLFilter.class.getName());
		}
	}

	/** Run all defined filters. Assume logical AND. */
	public String filter(String urlString) throws URLFilterException {
		for (int i = 0; i < this.filters.length; i++) {
			if (urlString == null)
				return null;
			urlString = this.filters[i].filter(urlString);

		}
		return urlString;
	}
}
